The purpose of the Histopathology Facility (HF) is to facilitate research conducted by investigators with peer-reviewed funding at FCCC by providing them with technical processing of cells and tissues as well as helping in the interpretation of results. The Facility's Technicians and Pathologist play a major support role in numerous research projects at the Center and their contributions have been and continue to be of paramount importance in the establishment and characterization of human cancer and other disease models. The Facility prepares, processes, and assists in evaluating tissues derived from experimental protocols developed by investigators with peer-reviewed funding. Most of the projects involve animal models of human cancer that require complex histological and/or cytological processing to determine morphological alterations, as well as to localize cancer-relevant gene products. The most frequently utilized services of the Facility include: laboratory animal autopsy, fixation, embedding and sectioning of paraffin-embedded tissues (7,000-8,000 per year), unstained paraffin sections for immunohistocnemistry (IHC) and LCM (10,000-14,000 per year), cryomicrotomy (100-200 per year), special stains (500-700 per year), immunohistochemistry (2,500-3,500 per year), in situ hybridization (100-200 per year), autoradiography (100-200 per year), digital microphotography (1,000-2,500 per year), and interpretative histopathology (7,000-10,000 HE and IHC slides signed-out per year). During the last CCSG funding cycle we have seen a significant increase in all services rendered as exemplified by the doubling in number of embedded and sectioned tissues (110% increase) and in the immunohistochemical work (120% increase). Furthermore, during 2000-2004 we implemented new technology such as tissue microarray sectioning and a Web-based Experimental Histopathology database. The Histopathology Facility also provides support to the Laboratory Animal Health Facility in quality control and animal health monitoring activities, as well as processing support to the Tumor Bank and the Research Cytogenetics and Laser Capture Microdissection Facilities. The HF is used by 33 investigators with peer-reviewed funding in 10 different Programs from all three Divisions. Eighty-nine percent (86%) of its use is for studies supported with peer-reviewed funding.